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Submitted to: Journal of Crop Improvement
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 11/18/2011 Publication Date: 5/30/2012 Citation: Reddy, K.N. 2012. Weed control and yield comparisons of glyphosate- and glufosinate-resistant corn grown in rotation. Journal of Crop Improvement. 26:364-374. Interpretive Summary: Glyphosate-resistant and glufosinate-resistant corn weed management systems have both advantages and limitations. Scientist at Crop Production Systems Research Unit, Stoneville, Mississippi conducted a 6-yr field study to determine the effects of rotating glyphosate-resistant and glufosinate-resistant corn under reduced tillage conditions on weed control, soil weed seedbank, and yield. The four rotation systems were glyphosate-resistant (RRRRRR) and glufosinate-resistant (LLLLLL) corn grown continuously and in rotation (RLRLRL and LRLRLR) with two herbicide programs, postemergence-only herbicides (POST) and preemergence herbicides followed by POST (PRE + POST). Control of 13 predominant weed species in glyphosate-resistant and glufosinate-resistant corn was >95%, regardless of herbicide program with the exception of johnsongrass and yellow nutsedge. Johnsongrass and yellow nutsedge control was lower in continuous LLLLLL system compared to other rotation systems. Corn yields were similar regardless of rotation. The PRE + POST program gave higher yield than POST-only program in 4 of 6 years. Seedbanks for grasses and yellow nutsedge were higher in the POST-only program compared to the PRE + POST program. These results indicate that johnsongrass and yellow nutsedge control could be reduced in continuous glufosinate-resistant corn and could be mitigated by rotating with glyphosate-resistant corn. Technical Abstract: A 6-yr field study was conducted from 2004 to 2009 at Stoneville, MS to examine the effects of rotating glyphosate-resistant and glufosinate-resistant corn (Zea mays L.) under reduced tillage conditions on weed control, soil weed seedbank, and yield. The four rotation systems were glyphosate-resistant (RRRRRR) and glufosinate-resistant (LLLLLL) corn grown continuously and in rotation (RLRLRL and LRLRLR) with two herbicide programs, postemergence-only herbicides (POST) and preemergence herbicides followed by POST (PRE + POST). Control of 13 predominant weed species in glyphosate-resistant and glufosinate-resistant corn was >95%, regardless of herbicide program with the exception of johnsongrass [Sorghum halepense (L.) Pers.] and yellow nutsedge (Cyperus esculentus L.). Johnsongrass (71 to 100%) and yellow nutsedge (66 to 85%) control was lower in continuous LLLLLL system compared to LRLRLR, RLRLRL, and RRRRRR rotation systems. Yellow nutsedge control was higher with the PRE + POST (89 to 99%) compared to the POST-only (72 to 86%) treatment. In 2004 and 2005, corn yields were 27-35% higher in glyphosate-resistant compared to glufosinate-resistant corn, regardless of rotation, mainly due to differences in yield potential of two cultivars with different traits. When a corn cultivar stacked with both glyphosate-resistant and glufosinate-resistant traits was used in 2006-2009, corn yields were similar regardless of rotation. Between herbicide programs, PRE + POST program gave 5 to 10% higher yield than POST-only program in 4 of 6 years. The seedbank for yellow nutsedge and predominant grass and broadleaf weeds was not significant among the four rotation systems. Seedbank for broadleaves was similar in the POST and PRE + POST treatments. Seedbanks for grasses and yellow nutsedge were higher in the POST-only program (20.5 and 1.8 per core, respectively) compared to the PRE + POST program (9.5 and 0.4 per core, respectively). These results indicate that johnsongrass and yellow nutsedge control could be reduced in continuous glufosinate-resistant corn and could be mitigated by rotating with glyphosate-resistant corn. |
